HSC Survey Results

Scots Bay Survey # 9 Results from 25/08/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 25/08/2024 starting at 20:00:00, which was 3.12 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 9,206mt, and with turnover applied 6,810mt.

The true estimate will likely be lower than presented due to a large amount of speed-based noise that was unable to be separated from biomass.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
C1 T01 2024-08-25 19:46:34 2024-08-25 22:51:25 -65.247 45.031 -64.715 45.205 SB 47.54 8.33
C1 T02 2024-08-25 23:11:42 2024-08-26 02:02:25 -64.743 45.255 -65.227 45.091 SB 43.37 8.23
FM T01 2024-08-25 20:41:00 2024-08-25 23:54:10 -65.235 45.076 -64.765 45.232 SB 41.29 6.92
FM T02 2024-08-26 00:14:42 2024-08-26 02:33:07 -64.790 45.282 -65.233 45.129 SB 38.87 9.10
LJ T01 2024-08-25 19:44:55 2024-08-25 23:09:34 -65.238 45.046 -64.708 45.223 SB 46.22 7.32
LJ T02 2024-08-25 23:28:56 2024-08-26 02:04:15 -64.755 45.263 -65.232 45.103 SB 41.57 8.67
MS T01 2024-08-25 19:41:44 2024-08-25 23:18:18 -65.219 45.068 -64.753 45.222 SB 44.82 6.70
MS T02 2024-08-25 23:45:05 2024-08-26 02:28:19 -64.781 45.271 -65.215 45.122 SB 39.03 7.75

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
FM T01 -35.5 -48.661 0.048
MS T01 -35.5 -51.090 0.028
MS T02 -35.5 -53.006 0.018
FM T02 -35.5 -53.296 0.017
LJ T01 -35.5 -53.418 0.016
C1 T01 -35.5 -54.470 0.013
LJ T02 -35.5 -55.206 0.011
C1 T02 -35.5 -57.593 0.006
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 475.7407 -52.633 0.0195 9,206.065 100 100 2,219.7 24.11

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by MS, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by FM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,745 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,283 17,575 17,387 16,022
Scots Bay 6 2024-07-15 4,539 3,560 2023-07-30 4,550 1,904 3,474 1,093
Scots Bay 7 2024-07-29 32,655 32,016 2023-08-13 4,299 3,616 2,777 2,247
Scots Bay 8 2024-08-11 15,213 10,296 2023-08-27 2,897 2,300 1,612 1,224
Scots Bay 9 2024-08-25 9,206 6,810 2023-09-10 3,054 2,916 3,219 0
Scots Bay 10 NA NA NA 2023-09-24 3,420 2,997 2,318 0
Scots Bay 11 NA NA NA 2023-10-09 3,388 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,538 204,189 218,266 177,329
2024 Scots Bay 304,520 263,523 NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number SB2024-15 SB2024-16
Ground SB SB
Date 25/08/2024 25/08/2024
Wind Direction (km/h) W W
Swell (m) 0 0
Air Temp (c) 24 24
Tow Details
Tow Start 17:58:00 18:14:00
Tow End 18:08:00 18:24:00
Start Lat 45.05217 45.05867
End Lat 45.0585 45.0510
Start Lon -65.22650 -65.21817
End Lon -65.2225 -65.2210
Avg Tow Depth (m) 1.274487 1.274487
Speed 2.4 2.7
Heading 21 194
Tide Direction against with
Other Data Collection
Flow Start 544521 575434
Flow End 575434 599444
No. Revolutions 30913 24010
Distance (m) 830.7250 645.2207
Volume 2609.723 2026.961
Secchi Disappear (m) 8 8
Secchi Reappear (m) 7 7

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-15, which was against the tide and had an average depth of 1.2744873m. The second tow is SB2024-16, which was with the tide and had an average depth of 1.2744873m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

The vessels performed well and the average vessel speed was 7.88 which is below the requirements of 8 knots.

The speed for each transect are rudimentary and are calculated based on distance. If a significant amount of distance is cut, the speed will appear slower.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.